The aim of the present study was to develop a method for identification of strains of Serratia marcescens that is also suitable for use in the epidemiologic studies. 40 clinical strains of Serratia marcescens were investigated by using the polymerase chain reaction (PCR). We used primers to amplify spacer regions between the 16S and 23S genes in the prokaryotic rDNA genetic loci. When the spacer amplification products were resolved by electrophoresis, the resulting patterns could be used to distinguish all of the strains tested into 3 groups (group A-35, group B-3 and group C-2 isolates). Digestion of PCR fragments of the group A strains with HinfI enzyme enabled separation of organisms into 3 distinct groups (A1-A3).